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We describe the changes in plant cover, species richness, and flowering after rainfall over an entire growing season (September 1989–January 1990) in a southern Atacama Desert site in Chile. One month after the rain, vegetation was dominated by annuals and geophytes which dried out after 19 weeks. Among all species, including shrubs, we found differences of 4–10 weeks in the length and peak of the flowering period. The flowering sequence of the species belonging to the families Brassicaceae, Liliaceae, Onagraceae, and Asteraceae matched closely the sequences described for temperate plant communities, suggesting that this phenological character is phylogenetically determined. 相似文献
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Carrichtera annuaandAnastatica hierochunticaare two desert annuals, the seeds of which are dispersed by rain. The seed coat surface and cross-section structure of the dry seeds of these plants were examined by SEM. The seeds were wetted by placing them on natural saturated desert soil crust in Petri dishes. The Petri dishes were placed in a freeze-dryer when the upper part of the seed surface was still dry. This enabled study by SEM of the developmental stages of the mucilage, from the first stage until the full formation of the mucilage. We argue that the ecological significance of the mucilage differs in winter and summer. In winter the main effect is in water retention and soil particle contact, while in summer dew may allow damage repair and priming for the germination process. 相似文献
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Yitzchak Gutterman 《Journal of Arid Environments》2003,54(4):619-631
This study examined dispersal units, caryopsis size groups, the inhibitory effect of loess soil on germination and the rate of germination of Schismus arabicus caryopses. Germination of small batches of the seeds from the large, long-lasting soil seed bank of S. arabicus contributes to its success as a very common annual plant in large areas of the Negev, under the unpredictable small amounts and distribution of rain. The lower the percentage of germinating caryopses on local loess soil, and the faster the speed of germination (from 4 h) of caryopses that do germinate, the higher is the chance of plants survival to reproduce. 相似文献
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在科尔沁沙地奈曼旗,大于10 mm的降雨属极端降雨。根据当地多年平均降雨量,设置雨量×降雨次数的双因素模拟试验(T1,共288 mm、分18次;T2,共288 mm、分9次;T3,共576 mm、分36次;T4共576 mm、分18次;CK,接收当年的自然降雨),考察极端降雨对科尔沁沙地一年生植被的密度、多样性指数、生物量及根冠比的影响。结果表明:(1)在萌发期,植株密度在各处理下均维持在2 000株·m-2;而在生长发育后期,T3、T4维持在400株·m-2,而TI、T2维持在1 600株·m-2,CK下为1 200株·m-2,说明降雨总量决定了能完成生活史的沙地一年生植被的数量。(2)T1、T2、T33种极端降雨模式均显著提高沙地一年生植被的生物多样性指数,说明科尔沁沙地一年生植被的生物多样性不是由年降雨量单一因素决定的,而是由每次降雨量与降雨次数的分布共同决定的。(3)T3、T4显著降低了沙地一年生植被的水分利用效率。 相似文献
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